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What is an Upper Respiratory Infection in Cats?

What is an Upper Respiratory Infection in Cats GraphicKitty colds, URIs, calicivirus, and more. Those are often the names given to feline upper respiratory infections. So what is an upper respiratory infection in cats?

Upper respiratory infections in cats are an infection of a cat’s sinus area, mouth or throat. These are basically ‘cat colds’ as their symptoms are similar to the everyday human cold. And just like human colds, most upper respiratory infections are caused by viruses, although there are a few other causes as well, such as bacteria, fungal and protozoa as well.

Upper Respiratory Infections in cats are a very common problem for anyone caring for multiple cats, especially outdoor cat colonies and barn cats, shelters, and breeding catteries.  This is something many caretakers and rescuers are familiar with.

Disclaimer: I am not a veterinarian, only an experienced cat caretaker, and this article does not constitute medical advice. This is for educational purposes only. Please consult your veterinarian for a specific diagnosis and treatment plan.

Disclaimer: Some links in this article are affiliate links. Simply put, I make a small commission on qualifying purchases. Read full Affiliate Disclosure for details! Thanks for supporting the kitties!

Symptoms of URIs

Upper respiratory infections can cause a wide array of symptoms. The most common signs of a URI include:

  • Clear or colored discharge from the eyes and/or nose.
  • Coughing
  • Sneezing
  • Conjunctivitis (swelling of the mucous membrane around the eyes)
  • Ulcers in the mouth
  • Anorexia
  • Lethargy
  • Fever
  • In rare cases, trouble breathing.

Magnification of Bacteria that May Cause Upper Respiratory Infections in Cats

Causes of Upper Respiratory Infections in Cats

The most common cause of feline upper respiratory infections is viruses. But bacteria, fungi, and protozoa can also cause an upper respiratory infection as well.

Viral URIs

The most common viral infections that cause URIs are the feline calicivirus and feline herpes virus. These two types of viral infections account for up to 90% of all upper respiratory infections in our feline friends.

Feline Calicivirus (FCV)

The feline calicivirus is a very common and highly contagious virus in cat populations throughout the world. According to Cornell University, 10% of cats in lightly populated areas are infected and up to 90% of crowded feline populations, such as shelters and breeding catteries, may be infected.

Signs of the Feline Calicivirus:

  • Upper Respiratory Infection symptoms such as sneezing, coughing, nasal discharge, etc.
  • Infection may spread to the lower respiratory system to cause pneumonia.
  • Viral pneumonia may be complicated by a secondary infection of the lungs, causing difficulty breathing.
  • Ulcers develop in the mouth in rare cases.
  • Rarely, limping may occur.

Very rarely, a more systemic form of the feline calicivirus may occur, which is fatal in 2/3s of all cats. The symptoms of the systemic feline calicivirus include swelling of the head and limbs, crusting sores and fur loss on the nose, eyes, ears, and footpads, yellowing of the mouth and ears (jaundice) due to liver damage, and even intestinal and subdermal (under the skin) bleeding may occur.

Diagnosis can be definitively determined only by a laboratory test done by your veterinarian.

Treatments for Feline Calicivirus:

  • Supportive care can be crucial while the cat fights off this virus.
  • Encourage the cat to eat and drink is absolutely vital, so if necessary, subcutaneous fluids may need to be administered or a feeding tube used if necessary.
  • Non-steroidal anti-inflammatories prescribed by your vet can help the cat’s oral pain if ulcers are present.
  • Saline drops or a saline solution in a nebulizer can help clear away some mucus to help the cat breath and smell better (which does help a cat to eat more!)
  • Medications to break down mucus can be prescribed by your veterinarian
  • Corticosteroids may be prescribed.
  • Antibiotics may be prescribed to fight off secondary infections

A cat’s recovery of a feline calicivirus infection depends upon the severity of the infection: it may take days, and it may take weeks. The systemic version of this virus causes death in 2/3rds of the cats who contract it.

Many cats who have been infected with the feline calicivirus remain infected for the rest of their lives. They may periodically shed this disease to other cats, even when they are showing no symptoms.

The feline calicivirus vaccine (FCV) is part of the core vaccine FVRCP that is given to all cats. As there are many variants of the calicivirus, though, this vaccine is not 100% effective at preventing infection, but vaccinated cats are less likely to catch the disease, their symptoms are milder, AND they don’t shed the disease as much once they are over the initial infection.

Feline Herpes Virus (FHV)Possible Upper Respiratory Infection in Cats Viral Agent

Young and immature cats are the most susceptible to this virus. Cornell University says up to 97% of cats have been exposed to FHV in their lives. 80% of those have a lifelong infection. Another 45% of those cats with an infection will periodically shed the virus, especially when stressed!

Signs of the Feline Herpes Virus:

  • Upper Respiratory Infection symptoms such as sneezing, coughing, nasal discharge, etc.
  • Ulcers on the cornea
  • Fever

Diagnosis is done by recognizing the reoccurrence of conjunctivitis of the eyes or corneal ulcers and various respiratory signs in older cats not exposed to a new cat or by laboratory tests.

Treatment for FHV:

  • Supportive care is crucial
  • Ensure the cat eats and drinks, and if necessary administering subcutaneous fluids or a feeding tube.
  • Antiviral medications may be prescribed to manage the severity or reoccurrence of FHV
  • Antibiotics may be prescribed to help prevent or clear up secondary infections
  • Nasal decongestants or corticosteroids may be prescribed
  • Lessening stress on the cat and thus reducing the severity and reoccurrence of the symptoms

Sometimes something called lysine is suggested as a supplement to help boost a cat’s immune response to this lifelong viral infection. This supplement is actually quite controversial as the studies regarding lysine supplementation and feline herpes virus show no evidence it helps suppress the virus or a cat’s immune response to it. In fact, some studies suggest it actually makes things WORSE and even causes shedding of the virus to worsen.

For the record, I do not recommend lysine supplements. So use it at your own risk.

Once infected with FHV, the cat is infected for life and may have periodic periods of upper respiratory symptoms and eye disease, especially in times of stress. These are usually minor flare-ups, and clear up on their own, but it can lead to death in very rare cases where infection leads to more serious illness.

FHV is commonly called feline viral rhinotracheitis (FVR) and is included in the core vaccine called the FVRCP vaccine. It doesn’t prevent all infection, but it significantly prevents most, reduces symptoms of infection, and reduces the shedding of the virus in infected cats.

Bacterial URIs

There are a few types of common bacterial infections that can cause upper respiratory infections in cats.

Feline Chlamydiosis

Chlamydia felis is one common bacterial infection of cats. These bacteria cannot survive outside of its host (the cat) and thus only contagious by close contact. C. felis is spread by eye secretions. It occurs most often in young cats and cats in crowded situations such as shelters and breeding catteries.

According to Cornell University, up to 20% of cats with upper respiratory symptoms have feline chlamydiosis and 3% of healthy cats carry it.

Signs of Chlamydia felis infection, include:

  • Eye conjunctivitis is the usual sign
  • Eye discharge that is clear at first, but later contains mucus and turns a yellowish appearance.
  • Rarely, anorexia or lethargy may appear.

Diagnosis can be done by your veterinarian either by eye swabs or testing for antibodies in unvaccinated cats.


  • Antibiotics such as Clavamox or clindamycin may be prescribed.

Antibiotics can completely cure the infection.

A vaccine is available for C. felis but is highly controversial as it isn’t that effective, it doesn’t seem to last long, and has a greater risk of side effects. It may only be considered in cats living in crowded catteries or such.

Black Kitten Awaiting Adoption in an Animal Shelter

Bordetella Bronchiseptica

This bacteria causes upper respiratory infections and is prevalent in highly populated shelters and breeding catteries. In these populations, about 5% of cats with upper respiratory symptoms are infected with B. Bronchiseptica and 1.5% of cats in shelters or catteries with no symptoms, according to Cornell University.

Infections are spread through oral and nasal secretions and symptoms range from mild to life-threatening, especially in young cats. Dogs can spread the infection to cats. Rarely, cats and dogs can even infect people with this bacterial infection.

Signs of Bordetella in Cats:

  • Coughing
  • Sneezing
  • Eye discharge
  • Difficulty breathing
  • Blue-tinged mucous membranes
  • Death

Diagnosis can be made in laboratory tests, although false negatives can occur.


  • Antibiotics such as doxycycline
  • Supportive care such as fluids and maintaining adequate nutrition.

With treatment, the prognosis is great from uncomplicated Bordetella infections in cats. Without treatment, the disease may progressively worsen and lead to pneumonia and death.

A vaccine is available for cats getting boarded or living in catteries, though it is not a core vaccination as most cats do not need it.

Fungal URIs

These upper respiratory infections are rarer and must be diagnosed by a lab done at your veterinary clinic. One type is more common than the rest, Cryptococcus neoformans.

Symptoms of C. neoformans:

  • Nasal and facial swelling
  • Sneezing
  • Chronic nasal discharge that may become bloody
  • Ultimately, wounds will not heal and the cat may develop fleshy polyp-like growths in their nose or throats.
  • Change in their vocalization sounds
  • Snoring or noisy breathing
  • Anorexia or weight loss
  • Rabid or labored breathing in some worsening cases
  • Infection may spread to the nervous system or skin and throughout the rest of the cats organs.

The most common cause of this fungal infection is bird droppings and decaying plant matter. Pigeons are a common cause.

This infection is diagnosed at your veterinary clinic by a blood sample or similar. X-rays, MRIs, and other imaging tests may be run to determine how far the infection has spread and how well the cat is responding to treatment.


  • Antifungal medications prescribed by your veterinarian

If caught early, the prognosis is good. Treatment for more advanced cases can last months or even years.

The only way to prevent this infection is to keep your cat indoors. For feral and community cats, that isn’t often an option, unfortunately.

Other types of upper respiratory infections in cats

There are many other types of infections that cause upper respiratory infections in cats, such as some avian or canine influenza viruses. Other types of infections include Yersinia pestis, a bacterial infection that is responsible for the “Black Plague” but is found mostly in rodents in the southwest United States and transmitted by fleas. Toxoplasma gondii, a protozoan infection cats often carry, can cause some upper respiratory symptoms. Lastly, Pasteurella multocida, a normal bacteria in feline respiratory systems may cause secondary infections.

Colony Cat Quarantined with an Upper Respiratory Infection

Symptoms of URIs in Cats

  • Sneezing
  • Coughing
  • Nasal discharge, clear to discolored
  • Eye discharge, clear to discolored
  • Inflammation of the soft tissue around the eye: conjunctivitis
  • Lost voice or hoarse sounding voice
  • Anorexia
  • Lethargy
  • Fever

Specific viral and bacterial infections have their own set of symptoms that are common to each one, but just because a cat is limping does not mean they have a calicivirus and just because a cat has a calicivirus does not mean he will start limping.

What is important is to recognize the signs of an upper respiratory infection in cats and to carefully monitor the cat to take to the vet when it becomes necessary.

As I stated previously, most URIs are viral and supportive care may be the only thing necessary to make sure the cat recovers. In other cases, you will need a veterinarian to prescribe you medication.

When to Seek a Veterinarian

If your pet is sick or acting differently, absolutely take your cat in to see the veterinarian. Best safe, than sorry!

However, feral cat caretakers may not always have this option. Especially when the stress of trapping and transporting a feral or semi-feral cat to the vet might do more harm than good. Between the stress of a veterinary visit and possibly sedation for the truly untouchable cats, sometimes it may be better to seek your veterinarian’s advice instead of taking your feral friend in to be seen.

Most upper respiratory infections are often mild and uncomplicated as long as the colony is fixed and the level of stress is low. However, secondary infections can lead to severe illness and even death, so pay attention to the sick cat.

DO seek out a veterinarian when cats are displaying these symptoms:

  • Difficulty breathing
  • Labored or rapid breathing
  • Lethargy
  • Anorexia or rapid weight loss
  • URI lasts longer than a couple of weeks
  • Heavy nasal discharge that is bloody or grossly discolored
  • Conjunctivitis (Red and inflamed eyes are no joke!  Untreated, this can lead to scarring, reduced sight or even a ruptured eyeball needing to be surgically removed.)

In some cases, they can do an antibiotic injection that will help a cat get well without you having to give daily medications. This is useful for feral and unsocialized cats.

Other Treatment Options

Along with your veterinarian’s suggestions, of course, you can try these things to help ease a cat suffering from an upper respiratory infection:

  • Saline drops in the nose to break up mucus
  • The saline solution in a nebulizer to help break up mucus and allow easier breathing
  • A single drop of Neo-Synephrine (found at any drug store) in each nostril can be helpful for severely congested cats.  Consult your veterinarian.
  • Humidifier or take the cat into the bathroom and run the hot shower for a while a few times a day
  • Vaseline (unscented) can be applied to their sore noses
  • Saline solution, like for contacts, can be used to clean out goopy eyes.
  • Use unscented baby wipes to clean off their face and clear crusty snot off their noses.
  • Heat up wet food or chicken baby food or buy the stinkiest fishy foods you can to encourage cats to eat.
  • Add water to wet food to ensure adequate hydration as almost all cats with upper respiratory infections will become dehydrated
  • If a cat still refuses to eat, a nutrient or high-calorie gel may be used.

If you want to go more of a homeopathic way, you could try things like raw apple cider vinegar to help boost the immune system or other suggestions. I suggest visiting Thriving Cat for information on that if you’re interested.

Sick Cat Resting in Owner's Bed

Other Tips

If you’re like me and care for a colony of community cats living outside, you have probably already come across the dreaded upper respiratory infection by now. In fact, we may be considered experts after a few years.

However, if you’re new to feral colony management or been extremely lucky to have never run into these fun kitty colds, here are a few other useful tips:

  • Quarantine the sick cat to prevent further infection, if possible.
  • Vaccinating your entire colony with more than just rabies would help prevent URIs (if possible). This is not 100% effective, but it does help lessen the severity and duration of a URI in a vaccinated cat if they catch it.
  • Kittens need to see a vet IMMEDIATELY. Do not wait. Kittens do NOT have a strong immune system!
  • Spay and neutering your colony (or Trap-Neuter-Return) will help to reduce the instances of feline upper respiratory infections greatly because it reduces the stress of the entire colony and decreases close contact since they aren’t mating or fighting anymore
  • If you can’t afford to get multiple feral cats seen by a veterinarian, you could use Alley Cat Allies’ Feral Friends Network to find a feral cat-friendly veterinarian near you that may be able to suggest some course of action.

Questions? Concerns? Ideas? Leave a comment below!


16 thoughts on “What is an Upper Respiratory Infection in Cats?”

  1. A most interesting article and it seems that if cats catch the flu it is much more detrimental than if humans do.

    I also learned something new today as never realised there was such a thing as Feline Herpes. I just wondered how cats catch this? You say over 80 per cent of the cat population is infected or carries the virus?

    Reading this article makes me quite scared of all the things that can go wrong with cats, but I suppose this isn’t as common in real life, and in most cases, cats will live to be a ripe old age.

    1. Hi! It is not 80% of the total population of cats! It is 80% of cats with upper respiratory infections are caused by calicivirus or the Herpesvirus, usually calicivirus. 

      If you have an indoor only cat or two, chances are they’ll never be infected by a kitty cold. Multicat households and shelters, as well as outdoor cats are the most commonly infected cats.

  2. It’s good to know that cat colds can be common for those who have a group of cats. This relieves some of the anxiety for the cat owner. Also good to know are the symptoms such as conjunctivitis, ulcers in the mouth, anorexia and trouble breathing. Not only have you provided excellent background information on upper respiratory infections, you have also provided treatments, which is very valuable information to have. I know some cat owners who will find this information as helpful as I have, and I will definitely share your post with them. Thanks and keep up the good work!

  3. There was a time when my cat seemed to be sick. She used to be so responsive and playful and loved to snuggle up with the kids, but then we noticed she kind of isolated herself and didn’t eat much of her meals. She would drink a lot though and we gave her liquid nourishment. After a visit to the vet and treatment with some medication she gradually came back to her usual self. I remember the vet saying that she had some kind of infection and her immune system was low. He also said we should have taken her in to see him earlier. I agree with you. When the pet doesn’t seem to be doing well, take her to the doctor as soon as you can. Thanks for this article.

  4. The calicivirus should never be taken lightly. Though most of the cases in cats involving the FCV might be mild, it is certainly not advisable to let it linger as severe cases might be terminal to the cat. I think the safest approach for cat owners would be giving their pets the FVRCP vaccination.

    1. It is of course always best for pet owners to vaccinate their cats. It is even more important that they keep their cats inside.  But people often take in strays, care for feral cats, or for shelters and rescues, they have unvaccinated cats coming into the shelter. Also not all upper respiratory infections are prevented by the vaccine. It’s always best to be informed, especially if you care for community cats, which is mostly why this post was created. A vet is always the best idea, but if you are caring for feral cats you don’t own, that isn’t always possible. 

  5. Interesting post.  I really like how you seem to cover so much territory with this information.  The part about how you can treat this I think was very good. I was just reading another of your posts about Lysine as well.  It’s good to know this sort of information is being distributed as seems like a quite common thing.

  6. Hello Rochelle, 

    I haven’t known what URI was to this day or heard about it. You’ve explained it thoroughly for those who are not familiar with this infection. I have a close friend who has 5 kittens and one of them had breathing issues, so forwarding this blog to him would be very informative and maybe life-saving.

    I appreciate you for taking the time to create this valuable content.

  7. Just want to warm everyone to avoid the Covenia antibiotic injection. It is the long acting one that your vet may suggest. If your cat has an adverse reaction to it, there is no way to get it out of her body. It will remain active, destroying her liver, etc for weeks. Please please please do not subject your cat to this. Most vets are unaware of how dangerous it is. I lost two cats to it before discovering this. Our pharmaceutical companies DO NOT have our best interest in mind.

    1. Hi, Kitty,

      I am sorry for your loss. It sucks to lose our beloved cats.

      While this is technically true, it doesn’t mean we should be vilifying a medication. Convenia is a very useful, effective, and relatively safe medication. But no medicine, supplement, or food is 100% guaranteed safe.

      Unfortunately, with all medications, preventatives, supplements, and even foods, there is a small risk of an adverse or allergic reaction.

      And you’re right because it is in your cat’s body for a long period of time IF there is a bad reaction it can become very dangerous and shouldn’t be used in cats that take oral medications easily. I myself had a cat with a possible bad reaction to it and he had to be hospitalized. But we do NOT know for 100% sure that it was the Convenia.

      But I’ve also had over 100 cats given this medication with ZERO problems. My vet has seen only my ONE reaction to that medication out of the thousands they’ve given, and we can’t say for sure it was the Convenia as it was simply a lack of appetite and lack of appetite is a common symptom in cat illness of ALL kinds and he was already sick. So we can’t prove his not eating for weeks and requiring force-feeding is because of the medication or because of his illness.

      So absolutely, if another medication can be given easily and is just as effective, Convenia shouldn’t be used. But if we’re talking about feral cats you can’t get to take the medication in their food or cats that are extremely bad about taking medication to the point of severe stress or violent outbursts, then Convenia IS a good option.

      And all possible adverse reactions need a vet immediately.

      Convenia isn’t bad. It has a low adverse reaction rate. Like less than 1% has severe adverse reactions. So sometimes the benefits of Convenia outweigh the POSSIBLE risk of taking it.

      Peanuts can kill human beings. We don’t say, “Peanuts killed my son, don’t eat them!” We know there is a risk of allergic reaction but it’s such a small chance that you let your kids eat peanut butter. Medications are the same. Supplements are the same. Flea medications and worm medications are the same.

      Convenia should absolutely be used only when it’s necessary for cats that aren’t easily medicated, but it is a great medication for feral or fractious cats. Better a small risk of a bad reaction than the suffering or death from illness or infection.

      If they discover the adverse reaction rate is much higher than the pharmaceutical company reported, then the FDA will pull the medication or add new warnings to the medication, as ALL pet or human medications are very tightly regulated. I don’t have any faith in ANY business as a whole as most just care about making money, whether it’s pharmaceutical companies, those scammy supplement companies, insurance companies, etc. But luckily, we DO have oversight from the government to make sure they meet safety standards before they can be released to the public. And it’s a terrible business to have a product killing off your patients/customers too.

      It does suck that there’s no such thing as 100% safe medications, though. And I’m sorry for your loss.

  8. Thank you for this information.
    As someone who is relatively new to being a caretaker for a small colony of cats I am interested in learning whatever I can to help them.
    One of my cats recently had an injury. I took him to a vet and he required surgery to repair the wound. I have kept him isolated inside. He was doing really well after the surgery for 5 days and then started showing signs of a “cold”. Sneezing and nasal congestion. He’s still eating well. I am taking him back to the vet tomorrow to get his stitches removed and have him checked out for the illness. In the meantime I am using a vaporizer to help with his congestion.
    I hope I am doing enough. It’s hard because while he’s not “my” cat… I don’t know his history like I do with my one indoor cat… I want to do everything possible to help him.

    1. Hi, Melissa!

      Thank you for taking care of him so well! Unfortunately, with URIs, they’re almost exactly like human colds in most cases, just something the cat will have to get over on his or her own. However, if it evolves into green/yellow mucus and severe illness, antibiotics would be needed. And using a vaporizer is fantastic for kitty colds! It’s exactly what many of them recommend to help break up the mucus. Good call on that.

      And thanks again for caring for him and I hope he recovered well!

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